Conversion of analog images into digital data has become widespread for a variety of applications, including storing, manipulating, transmitting and displaying or printing copies of the images. For example, images captured in photographic media are being converted to digital data and stored on compact discs for readout and display as a video image or for printing with various types of color printers. In order to capture the photographic image digitally, the image frame is scanned with a light beam or line, and the light transmitted through the image is detected, typically as three primary color light intensity signals, and digitized. The digitized values may be formatted to a standard for video display and stored on compact disc or magnetic media. Such film digitizers take a variety of forms and the various common aspects of film digitizing, particularly line illumination and linear CCD-based digitizers, are described in greater detail in commonly assigned U.S. Pat. No. 5,012,346.
In order to perform line scanning of an image frame of photographic filmstrips, it is necessary to provide an accurate film transport mechanism to transport a filmstrip into a scanning gate and hold the image frame flat in alignment with a scanning aperture. Typically, the linear CCD array and scanning light beam are stationary so that the light beam illuminates a line of the filmstrip image frame, and a line of digitized data is stored. The scanning gate is incrementally moved line-by-line until the entire image frame is digitized. Then a new image frame is positioned and flattened for scanning and digitizing. Such a scanning and digitizing system for Photo-CD conversion is embodied in the KODAK.RTM. PIW Model 2400 Photo-CD scanner system marketed by the assignee of this application.
In this film scanner, the scanning plane is vertical and the stationary scanner components are oriented horizontally. A translation stage advances the film scanning gate past the stationary scanner components in a first pass for scanning the clamped image frame at a low resolution sufficient to provide a video display of the image frame on a monitor for viewing by the operator. The color balance of the scanned and digitized image pixel data is automatically adjusted to the color balance characteristics of the video display. The operator may further adjust the displayed color balance or tone and intensity of the color display while viewing the result of the adjustments until satisfied, whereupon the adjustment factors for that image frame are stored. The orientation of the image may also be stored with the digitized data so that the CD player can rotate the image data 90.degree. for display as a video image at the same aspect that the image was captured by the photographer.
As each image frame is scanned in this first pass, the scanned image frames of the vertically oriented filmstrip are advanced into a stationary take-up chamber. The take-up chamber is provided within the scanner to temporarily hold the filmstrip and isolate it from other apparatus that it could catch on and to keep it clean. After all image frames are scanned, the trailing end of the filmstrip is retracted from the chamber and advanced in the reverse direction into the scanning gate one frame at a time. Then each image frame is scanned at high resolution for digitizing the image as a field of data associated to the data derived in the low resolution scan of the same image frame. The filmstrip is transported out the exit of the translation stage for removal by the operator when scanning of all frames is completed.
The relatively large, hollow, circular, take-up chamber has no moving parts and is fixed in position in the transport path with a film receiving slot positioned adjacent to an end of the translation stage. The filmstrip entering its slot is advanced and retracted during and between each scanning cycle through the movement of the translation stage. This movement can cause foreign particles, e.g. dust, to enter the chamber.
Within the interior cavity of the take-up chamber, the filmstrip is unrestrained and coils up against itself and the chamber walls. Since the filmstrip can tangle or catch in restricted spaces, e.g. the slot, friction may be introduced in the transport path that affects the proper centering of the image frame in respect to the scanning aperture and flattening of the image frame during the incremental operation of the translation stage. The filmstrip could also be scratched or damaged when being pulled into or out of the chamber slot. The chamber is sized relatively large in order to minimize the binding and scratching of the filmstrip.
Problems to be Solved by the Invention--Accordingly, there is a need for a take-up chamber that is compact in order to take up less space and minimizes the possibility of filmstrip jamming, binding, scratching or contamination.